Promising further review, the think tank removes a study from its website linking pot clinics to a drop in crime rates, after sharp criticism from the city attorney's office.

Rand Corp.'s website has removed a controversial study that suggested medical marijuana dispensaries may help reduce crime in their neighborhoods, a decision that came almost three weeks after enraged Los Angeles city attorneys slammed the report and demanded an immediate retraction.

Warren Robak, a spokesman for the Santa Monica-based think tank, said Tuesday, "As we've begun to take a look at the report, we decided it's best to remove it from circulation until that review is complete."

The study came under intense assault by the Los Angeles city attorney's office, which has argued in court that crime associated with dispensaries is a key reason the city needs to limit the number. The office called the report's conclusions "highly suspect and unreliable," saying that they were based on "faulty assumptions, conjecture, irrelevant data, untested measurements and incomplete results."

Jane Usher, a special assistant city attorney, said she was gratified by Rand's decision. "We spoke up to Rand, and Rand heard us out over a handful of communications," she said.

In a Sept. 21 letter to Mireille Jacobson, a health economist who was the lead researcher, Usher and Assistant City Atty. Asha Greenberg demanded that the study be repudiated. "Until you publicly retract your work, we expect the Rand publication to be referenced nationwide, at incalculable avoidable harm to public health and safety," they wrote.

Jacobson and the other researchers compared crime reports from the 10 days before the city's medical marijuana ordinance took effect on June 7, 2010, with the 10 days after, when some of the more than 400 illegal dispensaries shut down. They found a 59% increase in crime within 0.3 of a mile of a closed dispensary compared to an open one. But they acknowledged that those results were subject to a large margin of error and said that increase could range from as low as 5.4% to as high as 114%.

The researchers hypothesized that dispensaries may increase security because they employ cameras and guards, generate late-night foot traffic, displace street sales and draw more police patrols.

Usher and Greenberg challenged the assumption that most dispensaries closed on that date and remained closed for at least 10 days, noting: "To our knowledge, no comprehensive effort was ever made by anyone, including Rand, to track and record the precise openings and closings."

They also questioned the study's time frame, writing, "We were also terribly troubled by your suggestion that a 10-day period of statistical review constitutes a relevant crime trend."

Usher and Greenberg also said the researchers failed to use "available crime statistics, which cover considerably more offenses than you charted." They noted that the researchers did not acquire data from the Los Angeles Police Department that they said could be charted by city block.

Robak said Jacobson was not available for comment. He said he was not sure when Rand would complete its internal review. "People are working on this expeditiously," he said.

He acknowledged that the city attorney's office was the most outspoken critic. "I'm unaware of anyone else who's been so pointed in their criticism," he said.

Rand has previously removed studies from its website while they were under review, Robak said, explaining: "It does not happen often, but there is precedent."

He informed the media of the decision and noted, "That is a part of the Rand ethic, if I may boast a bit."